Traffic generated in mobile networks has mostly been dominated by services that require human interaction, such as regular speech calls, web-surfing, sending MMS, doing video-chats etc. As a consequence, these mobile networks are designed and optimized primarily for these “Human Type Communication”, HTC, services.
There is an increasing market segment for Machine Type Communication, MTC, services that may not require human interaction. MTC services include a diverse range of applications, e.g., vehicle applications, gas and power meter readings, and also network surveillance and cameras. The amount of MTC and HTC devices could reach a total of almost 50 billion, by the year 2020.
With the introduction of MTC devices, the GSM radio access network is facing a rapid increase in the number of mobile devices accessing and communicating through the network. MTC devices are those devices supporting communications that are not human initiated. In order for mobile networks, such as GERAN and UTRAN, to have a capability to support a mass market for MTC applications and devices, it is important to optimize the ability in the mobile networks to support MTC communication. A very large number of the MTC devices are expected to operate in the packet switched (PS) domain where a large percentage can be expected to be active sending or receiving application payload at any point in time. The amount of PS traffic in a network is continuously and rapidly increasing.
One critical issue in a mobile network is the ability to distinguish and properly address a vast number of data communicating devices for the case of simultaneous data transfer on shared radio resources. The available addressing spaces may not be sufficient. One of the identifiers that may be a bottleneck in this respect is the so called Temporary Flow Identity (TFI) which is assigned by the network to each Temporary Block Flow (TBF) for the purpose of identifying a particular TBF and transmitted Radio Link Control/Medium Access Control (RLC/MAC) blocks associated with that TBF.
Each Temporary Block Flow is assigned a Temporary Flow Identity (TFI) value by the mobile network. An RLC/MAC block associated with a certain TBF is identified by the TFI together with, in the case of an RLC data block, the direction, uplink or downlink, in which the RLC data block is sent and in the case of an RLC/MAC control message, by the direction in which the RLC/MAC control message is sent and the message type.
Every time a Mobile Station (MS) receives a downlink data or control block, it will use the included TFI field to determine if this block belongs to any (there can be more than one) of the TBFs associated with that MS. If so, the block is intended for this MS, whereupon the corresponding payload is decoded and delivered to upper layers; otherwise the block is discarded. In the uplink direction, the behavior is the same, i.e. the Base Station Subsystem (BSS) uses the TFI value to identify blocks that belong to the same TBF.
The TFI value is unique among concurrent TBFs in the same direction, i.e., uplink or downlink, on all Packet Data Channels (PDCHs) used for the TBF. The same TFI value may be used concurrently for other TBFs on other PDCHs in the same direction and for TBFs in the opposite direction, and hence a TFI is a unique identifier on a given resource such as a Packet Data Channel (PDCH). This limits the number of concurrent TBFs and thus the number of devices that may share the same radio resources.
The existing TFI address space consist of 5 bits encoded as binary number in the range 0 to 31, which is typically provided to the mobile station MS by the network upon assignment of the TBF. The number of possible TFI values is limited by the available 5 bits, enabling 32 individual values. Thus no more than 32 different mobile devices can be addressed at once on a specific timeslot. This may appear sufficient, and has until now provided no significant limitation. Given the large percentage of MTC devices that can be expected to be active sending or receiving application payload at any point in time, significantly increasing the TFI addressing space is seen as being an important enhancement. There are a number of indicators that the TFI addressing space may be a limiter in the future.
As previously mentioned, it is more than likely that the PS traffic volume, and implicitly the amount of TBFs per TRX, will increase manifold. It is not an unlikely situation that it would be beneficial to multiplex dozens or more users on the same uplink PDCH. If a TBF is assigned to be used on more than one PDCH (which is most often the case) the number of usable TFIs per PDCH drastically decreases. Assume, e.g., that all TBFs are used on all 8 PDCHs. This means that the average number of TFIs per PDCH will be 32/8=4, as compared to the 32 TFIS per PDCH that would be the case otherwise. Since it may be desirable to spread a TBF over as many PDCHs as possible in order to improve the statistical multiplexing gain and flexibility, this has the drawback of reducing the potential number of TBFs that can be supported on any given set of PDCHs, such as e.g. a Transceiver (TRX).
With recent additions to the 3GPP standards which allow use of multiple TBFs associated with one and the same MS by means of Multiple TBF procedures, the number of TBFs associated with any given MS will no longer be limited to one per direction. One particular MS could now e.g. in the downlink have one TBF for a web-surfing session, another for an ongoing VoIP call (or an audio-streaming session with e.g. Spotify) and finally a third for a messaging service such as MSN. The benefit of splitting these particular services over different TBFs is of course that they all have different service requirements, but an obvious drawback is that more TFIs are needed.
SIEMENS “Outstanding issues of the multiple TBF concept”, 3GPP DRAFT; GP-011548 discloses a solution for addressing multiple TBFs wherein the TFI assignment field is modified to include more than one TFI value for multiple TBFs. However, the document does not address the problem of expanding the TFI addressing space in order to accommodate a need for additional amount of TBFs per TRX.
WO2011/099922 discloses a solution for enabling additional TFI addressing by expanding the addressing space for TFI values. The additional addressing space is achieved through a second group of TFIs comprising a TFI in the legacy addressing space together with information in the RLC/MAC block.
However, solutions for resolving a TBF in a mobile network with such an increased TFI addressing space have so far not been disclosed.